Valve mechanism for fluid pressure tools



' May 1-9, 1931. G. M. NELL VALVE MECHANISM FOR FLUID PRESSURE TOOLS Filed Aug. 23. 1928 INVEN TOR. 60s fan/e M A/el/ A TTORNE Y.

Patented May 19, 1931 UNITED STATES PATIENT oFFIcsv GusrAvE M. NE L, or DETROIT, MICHIGAN, ASSIGNOR T CHICAGO, PNEUMATIC 'rooL COMPANY, on NEW YORK, 1v. ACORPORATION OENEW masnv' valve in a different position; and

; VALVE MEcHANIs roRrLUID rnnssunn roots Application filed August 23, 1928. Serial No. 301,461.

This invention relates to fluid pressure motors of the reciprocating type, particularly those actuating a free flying piston arranged to have a percussive action. More particularly it relates to automatic valve arrange- .ments-for such motors when utilized for hammers and hammer'drills.

Among the objects of the invention are to devise an improved type of valve which is positively held in a given position, to so arrange the valve thatxthe pressure or pressures which cause its movement come from the piston chamber'and are'effected or controlled by the piston, to avoid perforations in the valve, and in general to simplify and to improve fluid pressure tools in the interest of increased efficiency and service. i

In order to illustrate the invention, one concrete embodiment thereof is shown in the accompanying drawings in which: 1

Fig. 1, is a longitudinal sectional view partly broken away;

Fig. 2, is a fragmentary sectional view similar to Fig. 1 showing the piston and Fig. 3', is a detail sectional view substantially on the line 3-3 of Fig. 2. V s

In the embodiment of the invention, chosen for the purpose-of illustration, afluid pres- .sure hammer drill is disclosed having a cylinder tproviding a piston chamber in which reciprocates a hammer piston 5 having an extension 5a arranged to impart blows to the shank end of a drill steel 6 which is suitably supported for this purposein a front head 7 secured to cylinder 1. The cylinder provides a valve chamber for an automatically thrown valve 8 which operates in timed relation with the reciprocations of piston 5 and controls the admission of motivefluid to the opposite ends of the piston chamber to drive the piston.

The particular form of valve herein shown,

istubular and has end areas of equal extent and a substantial centrally disposed stepped flange providing opposedholding areas 9 and 10 and opposed shift areas 11 and 12, the holding areas being of slightly greater extent than the shift areas. The cylinder provides continuously opened vent ports 11a and 1200f limited size forthe shift areas and cross ports 11?) and 12?) ex tending from the piston chamber-at opposite sides of a main piston controlled exhaust 5b. Motive fluid inlet passages 13 and 14 extend fromopposite ends of the'valve chamber to the proximate ends of the pistonchamber and arecoritrolled by the extreme ends of-valve 8. Suitable meansaa're provided for establishing and continuously maintaining communications between the holding areas 9, 10 of the valve and the adjacent inlet passages 13 and 14 for thepis ton chamber. In the present instance such means take the form ofaxially directed channels adjacent the outer surface of the valve.

and preferably formed in partitions provided by the cylinder-0r casing 4 between the holdmg areas of the valve and the respective end chambers of the valve. Such channels may 'be one or more in number.v By preference four areprovlded'as shown in Fig.3, the

channels leading from passage 13 to holding area 9 being indicated at 9a (Figs. 1 and 2) and those leading from passage 14: to holding area 10 being indicated at 10a (Figs. 1,2, and 3). i

The operation of the motor is as follows. Motive fluid enters the valve chamber through inlet 15 audits distribution therefrom to the tain the valve in the positionsho-Wnr All other areas of the valve are open to exhaust with the exception of the equal end areas of the valve which are always subject to the pressure of the live motive fluid. As the piston advances, it cuts off the main exhaust port 5?) but a portion of the air ahead of the piston can still escape through passage 12?) and valve vent 12a until the passage is closed. On further movement of the piston, passage 11?) is uncovered admitting motive fluid from the rearpiston chamber against shift area 11 of the valve. A portion of such'motive fiuid'passes at once to atmosphere through vent 11a butsince vents 11a and 12a are of much'smaller capacity than shift passages 11b and 12?), a substantial pressure builds up against area 11. This is insufficient, however, to shift the valve'becausehol'ding area 10 is of greater extent than shift area 11. After piston 5 covers passage 1%, the air *trappedin advance of the-piston is compressed and thispressure is communicated to the opp'osingholding area 9 through inlet passages 13 and channels 9a. When this 25 I the pressure against holding area 10, the pressure on shift'area 11' then preponderates pressure balances, or substantially balances,

and the valve is thrown to the position shown in Fig. :2. This shifting of the valve takes place about the time that main exhaust 5Zris uncovered or begins to be uncovered by p1ston 5. v

As the blow is struck or immediately thereafter, the parts are in the'position shown in Fig.2, the rearward or left'end areas 10 I and 12, as well as shift area 11, being open to exhaust while motive fluid is now admitted by valve 8'to passage 13 to drive the piston rearwardly. This admitted motive fluid is also effective against area 9, byreason of channels 9a, to hold-the valve in its shifted position. As the piston moves rearwardly, it first covers the main exhaust 5?) then admits pressure fluid through passage 12?) to shift area 12.

The valve is not thrown until the air compressed by the piston becomes effective through passage 14' andchannels 1064 against holdingarea 10 to put the valve in a state of substantialbalance. l/Vhen the valve shifts, the parts are substantially in the position shown in Fig. 1 and the cycle" of operations the holding areasfor the valve and the adjacent ends of the piston chamber.

'While the invention has been-herein disclosed in what is now considered to be a pre- 'ferred form, it is to be understood that the tent'than sai'd passages, said valve'having 'opposed'holding areas alternately effective to retain the valve in position, means maintainingsai'dholding areas continuously in communication with the opposite ends of said piston chamber, and means alternately subjecting said holding areas to live motive fluid.

2. A fluid pressure motor comprising "a cylinder, a piston reciprocable therein, and a'valve for controlling the 'motivefluid supply to operate said piston and moving alternately in timed relation'with the latter, said valve having opposed shift areas, vents'for said areas, supply passages thereto under control of said piston,said vents being of less extent than said passages, said valve having opposed holding areas alternately effective to retain the valve inposition, means maintaining said holding areas continuously in commmunication with the opposite ends of said piston chamber, at least a portion of said means being effective to direct a portion of the motive fluid admitted by said valve alternately to said holding areas.

3.- A fluid pressure percussive tool comprising a casing, providing a piston chamber and a valve chamber, a hammer piston reciprocable within said piston chamber, a valve automatically movable within 'said valve chamber in timed relation with said piston, said casing having ports and passages extend ing between said chambers and a main vent port for said-piston chamber controlled. by

said piston, said valve having opposed shift areas, said casing providlng supply passages to saidareas under control of saldpiston and continuously open vent ports of smaller extent than said supply passages, saidv valve having opposed holding areas of greater extentthan said shaft areas, and means maintaining saidholding areas in communication with the opposite ends of said piston cha1nber at all times and subject to the fluid pressure conditions obtaining therein. I

. 4. A fluid pressure motor ,comprising a cylinder, a piston reciprocable therein, an

imperforate motive, fluid controlling valve having a central shifting head, the ends of said valve controlling admission 'of'motive fluid to the cylinder, valve'position holding areas intermediate said central head and said extreme ends, piston controlled means for shlftlng said valve, and means maintaining communlcatlon between said holdlng areas and the ends of said cylinder. 7 Y

the latter, said partitions providing com munication between said areas and said admission chambers.

6. A fluid pressure motor comprising acylinder, a piston reciprocable therein, a

valve controlling the supply of motive fluid to opposite ends of the cylinder to actuate said piston, said valve having opposed shift areas and opposed holding areas, means controlled by said piston for admitting pressure fluid alternately to said opposed shift areas, and means utilizing air compressed by the piston toward the end of its stroke in one direction against one of said holding areas to assist in the shifting of said valve.

7. A fluid pressure motor comprising a cylinder, a piston reciprocable therein, a valve controlling the supply of motive fluid to opposite ends of the cylinder to actuate said piston, said valve having end areas continuously subjected to live'motive fluid, said valve also having a central stepped head providing opposed shift areas and opposed holding areas, the holding areas being of greater extent than the shift areas, means controlled by said piston foradmitting pressure fluid alternately to said opposed shift areas, and means utilizing air compressed by the piston toward the end of its stroke in both directions for substantially balancing the pressureon said holding areas.

8. A fluid pressure motor comprising a cylinder, a piston reciprocable therein, an

imperforate motive fluid controlling valve I having a central shifting head, the ends of said Valve controlling admission of motive fluid to the cylinder, valve position holding areas intermediate said central head and said extreme ends and of greater extent than the shifting areas on said central head, said cylinder providing partitions between the holding areas of said valve and the admission chaming areas being of greater extent than said shift areas, means controlled by said piston for admitting pressure fluid alternatelyto said shift areas, and means utilizing air compressed by the piston at the end of its stroke in one direction against one of said holding areas to assist in the shifting of said valve.

Signed by me at Detroit, in the county of Wayne, and State of Michigan this 15 day of August, 1928.

GUSTAVE M. NELL.

bers at the ends of the latter, said partitions providing communication between said holding areas and said admission chambers.

9. A fluid pressure motor comprising a cylinder, a piston reciprocable therein, a valve controlling the supply of motive fluid to opposite ends of the cylinder to actuate said piston, said valve having opposedshift areas and opposed holding areas, said hold- 

